Solid-state image sensors, in general, comprise a photodetector for detecting radiation from the image and converting the radiation to charge carriers, and transfer means for carrying the charge carriers to an output circuit. One type of solid-state image sensor uses a CCD as both the photodetector and the transfer means. The solid-state image sensor generally includes a plurality of the CCD's or pixels arranged in spaced parallel relation to form an area array. One problem which has arisen in this type of solid-state image sensor is known as "blooming." Blooming is a phenomenon that occurs when the number of charge carriers generated in a photodetector site by the incident radiation exceeds the storage capacity of the site. These excess charge carriers then spill over or "bloom" into adjacent photodetector sites thereby degrading and, in some cases, completely obliterating the integrity of the image.
To overcome this problem, various antiblooming structures have been developed and used in the sensors. One structure which has been used is a vertical-overflow drain which comprises a drain extending into the substrate in which the image sensor is formed into which the excess charge carriers flow. See U.S. Pat. No. 5,122,850.
Lateral-overflow drain (LOD) structures have also been used in solid-state image sensors. The lateral structure may comprise a drain which is positioned in the substrate in which the CCD is formed and extends along (i.e., laterally) a charge carrying channel region of the CCD. See U.S. Pat. No. 5,130,774 to Stevens et al.